Image sensing module capable of fast transferring signal and method thereof

ABSTRACT

An image sensing module capable of fast transferring signal and a method thereof are proposed. The image sensing module comprises an optical sensor set, a plurality of readout circuits and a plurality of amplifying circuits. Each readout circuit has a plurality of input terminals and an output terminal. Each amplifying circuit has an input terminal and an output terminal. The input terminals of each readout circuit are connected with the optical sensor set. The output terminal of each readout circuit is connected to the input terminal of one of the amplifying circuits. These readout circuits simultaneously capture output signals of the optical sensor set and then transfer to corresponding amplifying circuits in a parallel way. These amplifying circuits then output the amplified signals one by one in an orderly and time-sharing way to accomplish quick transmission of signals of the image sensing module.

FIELD OF THE INVENTION

The present invention relates to an image sensing module capable of fasttransferring signal and a method thereof and, more particularly, to animage sensing module making use of optical signals for image detection.

BACKGROUND OF THE INVENTION

A contact image sensor (CIS) is a device which detects optical signalsand converts them into readable electric signals. It is applied in imageprocessing devices requiring electro-optical components for readingtexts and pictures data such as scanners and copiers.

As shown in FIG. 1, after a document (not shown) is fed onto atransparent glass 73 through a transmission axis 71, a light source 79will illuminate the document. The reflected light passes through alenticular lens 75, which proportionally projects the reflected imageonto a CIS chip 77 of a CIS module 70 in an identical ratio. The CISchip 77 then detects the light signals to output electric signals inorder.

The CIS module 70 is formed by series connecting several CIS chips 77 tomatch the size of a document to be read. That is, the larger the size ofa document to be read, the more the CIS chips 77 used on the CIS module70. The total length of the series-connected chips should be larger thanthe width of the document.

As shown in FIG. 2, a conventional image sensing module comprises anoptical sensor set 81, a switch array 83, a shift array 0.85 and anamplifying circuit 87. In this embodiment, the resolution of the opticalsensor set 81 is 600 dpi (dots per inch). In other words, the opticalsensor set 81 includes 600 optical sensors D1˜D600. The optical sensorsD1˜D600 can be photodiodes or phototransistors. The switch array 83 iscomposed of 600 switches, which are connected to the output terminals ofthe optical sensors one by one. The switch array 83 is used forcontrolling transmission of charge signals accumulated by the opticalsensors. That is, after any optical sensor accumulates an enough chargeenergy, the corresponding switch will be on. The shift array 85 iscomposed of shift registers of the same number as the switches. Theshift array 85 is used to respond to the input of a timing signal CK tocontrol in order the activation of corresponding switches so thatsignals in the optical sensors can be outputted in order according topixel positions.

The amplifying circuit 87 is connected to the output terminal of theshift array 85. The amplifying circuit 87 comprises an operationamplifier (op_amp), two switches SW1 and SW2, and a capacitor CL, and isused to amplify the output signal of the shift-array 85 for subsequentread and processing. The scanned image signals can thus be obtained.

For an existent CIS, the readout of signals is accomplished byaccumulating sensed optical signals in optical sensors in charge form.The accumulated charges are then outputted one by one when outputtingpixels. For the architecture shown in FIG. 2, the produced timingdiagram is shown in FIG. 3. Through control of the on time of theswitches SW1 and SW2, each charge signal outputted by the shift array 85can be outputted and amplified in order, and a reset time (controlled bythe switch SW2) is provided between adjacent charge signals. After thereset is finished, the next charge signal of the shift array 85 is thenoutputted.

When the signal of an existent CIS is read, charge signals obtained bydetecting light using optical sensors are outputted one by one. Thehigher the resolution, the more the optical sensors used. Therefore, inorder to completely output the charge signals of all the opticalsensors, the required time is elongated. For the architecture of anexistent image sensing module, if the speed of signal output is to beincreased, one can raise the clock of the shift array to fast switch theconduction time of each optical sensor for outputting the charge signal.

Although shortening the conduction time of each optical sensor foroutputting the charge signal can speed up the signal output of the imagesensing module, there is still a bottleneck to completely output thecharge signals accumulated by the optical sensors in such a short timedue to the charging/recharging time of capacitor, which is furtherlimited by the area size of the optical sensors and the detectioncapability in an unit time.

Accordingly, the present invention aims to provide an image sensingmodule capable of fast transferring signal and a method thereof to solvethe above problems in the prior art.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image sensing modulecapable of fast transferring signal and a method thereof, which cansimultaneously capture charge signals of several optical sensors toaccomplish quick transmission of signals.

To achieve the above object, the present invention provides an imagesensing module comprising an optical sensor set, a plurality of readoutcircuits and a plurality of amplifying circuits. The optical sensor sethas a plurality of optical sensors used for receiving an optical signaland generating a plurality of corresponding charge signals. Each readoutcircuit has a plurality of input terminals and an output terminal. Theinput terminals of each readout circuit are connected with the opticalsensors. The output terminals of the readout circuits output in orderthe charge signals received by the input terminals of the readoutcircuits. Each amplifying circuit has an input terminal and an outputterminal. The input terminal of each amplifying circuit is independentlyconnected to the output terminal of one of the readout circuits. Theinput terminal of each amplifying circuit receives and then amplifiesone charge signal outputted in order by the output terminal of one ofthe readout circuits. The output terminals of the amplifying circuitsthen output in order the amplified charge signals.

To achieve the above object, the present invention also provides animage sensing method capable of fast transferring signal. This imagesensing method comprises the steps of: providing m charge signals bydetecting light; dividing said m charge signals into n sets of outputsin a discontinuous order; capturing said charge signals of each set atthe same time; and outputting said captured charge signals in an orderlyand time-sharing way.

The various objects and advantages of the present invention will be morereadily understood from the following detailed description when read inconjunction with the appended drawing, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a conventional CIS module;

FIG. 2 is an architecture diagram of a conventional image sensingmodule;

FIG. 3 is a timing diagram of a conventional image sensing module;

FIG. 4 is an architecture diagram of an image sensing module of thepresent invention; and

FIG. 5 is a timing diagram of an image sensing module of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 4, an image sensing module of the present inventioncomprises an optical sensor set 11, four readout circuits 13, 15, 17 and19, and four amplifying circuits 21, 23, 25 and 27. In this embodiment,the optical sensor set 11 includes 600 optical sensors D1 a˜D600 a. Theoptical sensors are photodiodes or phototransistors. These opticalsensors are used to receive an optical signal obtained by detecting animage and then generate a plurality of corresponding charge signals.

The insides of the four readout circuits 13, 15, 17 and 19 have the samesubassemblies and connection relationships, and each of them has aplurality of input terminals and an output terminal. For instance, thereadout circuit 13 has a switch array 131 and a shift array 133. Theswitch array 131 is composed of 150 switches, which are connected to theoutput terminals of the optical sensors one by one. The arrangementorder of the connected optical sensors is D1, D5, D9, . . . D597. Theseswitches of the switch array 131 are used to control transmission ofcharge signals accumulated by the corresponding optical sensors. Thatis, after an optical sensor accumulates an enough charge energy, thecorresponding switch will be on. The shift array 133 is composed 150shift registers, which are connected to corresponding switches of theswitch array 131 one by one. The shift array 133 is used to turn on inorder the corresponding switches of the switch array 131 connected tothe shift registers according to an input clock signal so that thecharge signals of the optical sensors (D1, D5, D9, . . . D597) connectedto the switches of the switch array 131.

Because the internal composition of the readout circuits 15, 17 and 19is the same as that of the readout circuit 13, it won't be furtherdescribed. The difference is in that the arrangement order of theoptical sensors connected to a switch array 151 of the readout circuit15 is D2, D6, D10, . . . D598, the arrangement order of the opticalsensors connected to a switch array 171 of the readout circuit 17 is D3,D7, D11, . . . D599, and the arrangement order of the optical sensorsconnected to a switch array 191 of the readout circuit 19 is D4, D8,D12, . . . D600. The outputs of the optical sensor set 11 are dividedinto four equal parts by the four readout circuits 13, 15, 17 and 19.The arrangement order of the optical sensors connected to each part isdiscontinuous. This is an important characteristic of the presentinvention.

Please refer to FIG. 4 again. The insides of the four amplifyingcircuits 21, 23, 25 and 27 have the same subassemblies and connectionrelationships, and each of them has an input terminal and an outputterminal. The input terminals of the amplifying circuits 21, 23, 25 and27 are connected to the output terminals of the readout circuits 13, 15,17 and 19, respectively.

The amplifying circuit 21 will be illustrated below. Because theinternal composition of the amplifying circuits 23, 25 and 27 is thesame as that of the amplifying circuit 21, it won't be furtherdescribed. The amplifying circuit 21 includes a first switch SW11, asecond switch SW12, a third switch SW13, a fourth switch SW14, anoperation amplifier OP1, a first capacitor C11 and a second capacitorC12. A first terminal and a second terminal of the first switch SW11 areconnected to the output terminal of the shift array 133 and a firstterminal of the second switch SW12, respectively. A second terminal ofthe second switch SW12 is grounded. A first terminal and a secondterminal of the first capacitor C11 are connected to the first terminalof the second switch SW12 and a negative input terminal of the operationamplifier OP1, respectively. A positive input terminal of the operationamplifier OP1 is grounded. A first terminal and a second terminal of thesecond capacitor C12 are connected to the negative input terminal and anoutput terminal of the operation amplifier OP1, respectively. A firstterminal and a second terminal of the third switch SW13 are connected tothe first and second terminals of the second capacitor C12,respectively. A first terminal of the fourth switch SW14 is connected tothe output terminal of the operation amplifier OP1.

Besides, a first terminal of a first switch SW31 of the amplifyingcircuit 23 is connected to the output terminal of the shift array 153, afirst terminal of a first switch SW51 of the amplifying circuit 25 isconnected to the output terminal of the shift array 173, a firstterminal of a first switch SW71 of the amplifying circuit 27 isconnected to the output terminal of the shift array 193. Secondterminals of the fourth switches SW14, SW34, SW54, SW74 of theamplifying circuits 21, 23, 25 and 27 are connected together.

The amplifying circuits 21, 23, 25 and 27 used in the present inventionare switching capacitance amplifiers. The first switches SW11, SW31,SW51 and SW71 are used for sampling to provide guiding paths so thatoutput signals of the shift arrays 133, 153, 173 and 193 can be storedin the first capacitors C11, C31, C51 and C71 on the series-connectedpath, respectively. Because the output paths of the shift arrays 133,153, 173 and 193 are different, there may be offsets between their DClevels. Therefore, the first capacitors C11, C31, C51 and C71 in thepresent invention have also the capability of pulling the DC levels ofthe shift arrays 133, 153, 173 and 193 to the same level to avoid leveloffset of the output signals. Besides, the magnification provided byeach of the amplifying circuits 21, 23, 25 and 27 is determined by theratio of the capacitance value of the first capacitor to that of thesecond capacitor.

In the present invention, the capacitance values of the first capacitorsC11, C31, C51 and C71 are larger than those of the second capacitorsC12, C32, C52 and C72 to provide magnifications larger than 1 and thuscompensate insufficient signal strengths transferred at high speeds formore convenient readability. During readout of the signals of theamplifying circuits 21, 23, 25 and 27, the first capacitors C11, C31,C51 and C71 will be destructively read and thus will be reset.Therefore, there will be no residual charge signals on the firstcapacitors C11, C31, C51 and C71 when the amplfying circuits 21, 23, 25and 27 receive the next output signals of the shift arrays 133, 153, 173and 193.

Besides, the first switches SW11, SW31, SW51 and SW71 and the thirdswitches SW13, SW33, SW53 and SW73 of the amplifying circuits 21, 23, 25and 27 have the same switching frequency and are synchronous,respectively. The output signals of the shift arrays 133, 153, 173 and193 can thus be simultaneously sampled to the first capacitors C11, C31,C51 and C71. The second switches SW12, SW32, SW52 and SW72 and thefourth switches SW14, SW34, SW54 and SW74 of the amplifying circuits 21,23, 25 and 27 have the same switching frequency and are synchronous,respectively. The second switches SW12, SW32, SW52 and SW72 of theamplifying circuits 21, 23, 25 and 27 have the same switching frequencybut are not synchronous. The fourth switches SW14, SW34, SW54 and SW74of the amplifying circuits 21, 23, 25 and 27 have the same switchingfrequency but are not synchronous. The amplifying circuits 21, 23, 25and 27 can thus output the amplified signals in an orderly andtime-sharing way.

The way of accomplishing fast transmission of signals will be describedin detail below.

First, the readout circuits of the present invention are divided intofour groups 13, 15, 17 and 19. The number of groups can vary accordingto practical necessity. A plurality of charge signals of the opticalsensor set 11 obtained by detecting light can thus be divided into fourparts and then outputted in parallel. There will be 150 charge signalsthat can be outputted by each part. The arrangement order of the opticalsensors connected to each of the readout circuits 13, 15, 17 and 19 isdiscontinuous. The readout circuit 13 will output in order the chargesignals of the optical sensors D1, D5, D9, . . . , D597. The readoutcircuit 15 will output in order the charge signals of the opticalsensors D2, D6, D10, . . . , D598. The readout circuit 17 will output inorder the charge signals of the optical sensors D3, D7, D11, . . . ,D599. The readout circuit 19 will output in order the charge signals ofthe optical sensors D4, D8, D12, . . . , D600.

After synchronous clock signals are inputted to the shift arrays 133,153, 173 and 193 of the readout circuits 13, 15, 17 and 19, the readoutcircuits 13, 15, 17 and 19 can simultaneously output the charge signalsof the correspondingly connected optical sensors. That is, the readoutcircuits 13, 15, 17 and 19 will simultaneously output the charge signalsof the optical sensors D1, D2, D3, D4, respectively. The next time, thereadout circuits 13, 15, 17 and 19 will simultaneously output the chargesignals of the optical sensors D5, D6, D7, D8, respectively. The readoutcircuits 13, 15, 17 and 19 will output the charge signals in this wayuntil the charge signals of all the optical sensors have been outputted.

The amplifying circuits 21, 23, 25 and 27 correspondingly connected tothe output terminals of the readout circuits 13, 15, 17 and 19 providethe functions of sampling and amplification. Through the control ofswitches in the amplifying circuits 21, 23, 25 and 27, the amplifyingcircuits 21, 23, 25 and 27 can simultaneously sample the charge signalsoutputted by the shift arrays 133, 153, 173 and 193 and then store themin the first capacitors C11, C31, C51 and C71, respectively. Next, theamplifying circuits 21, 23, 25 and 27 will amplify and output thesampled signals stored in the first capacitors C11, C31, C51 and C71 inan orderly and time-sharing way, respectively.

Please refer to FIG. 5, wherein CK represents a clock signalsynchronously inputted to the shift arrays 133, 153, 173 and 193, SW1and SW2 represents switching frequencies of a conventional sensingmodule, and Vout represents an output waveform of a conventional sensingmodule.

The way of accomplishing quick transmission of signals in the presentinvention will be illustrated for the period when each of the readoutcircuits 13, 15, 17 and 19 outputs a charge signal (i.e., a duty cycleof the clock signal CK). First, after the first switches SW11, SW31,SW51 and SW71 and the third switches SW13, SW33, SW53 and SW73 are onfor a period of time, the second switch SW12 and the fourth switch SW14of the amplifying circuit 21 are then simultaneously on for a period oftime to output the amplified signal of the shift array 133. Next, thesecond switch SW32 and the fourth switch SW34 of the amplifying circuit23 are simultaneously on for a period of time to output the amplifiedsignal of the shift array 153. The second switch SW52 and the fourthswitch SW54 of the amplifying circuit 25 are then simultaneously on fora period of time to output the amplified signal of the shift array 173.Finally, the second switch SW72 and the fourth switch SW74 of theamplifying circuit 27 are simultaneously on for a period of time tooutput the amplified signal of the shift array 193.

Please refer to FIG. 5 again. In the present invention, signals areoutputted with a duty cycle of the clock signal CK as the unit time. Theamplifying circuits 21, 23, 25 and 27 will circularly output the chargesignals of all the optical sensors one by one. Moreover, in a duty cycleof the clock signal CK, there are four output signal V'out of thepresent invention as compared to only one output signal Vout in theprior art. Evidently, the present invention has a better transmissioncapability per unit time than the prior art.

To sum up, in the present invention, the amplifying circuits 21, 23, 25and 27 are used to simultaneously capture four signals outputted by theshift arrays 133, 153, 173 and 193 and then output them in a speed fourtimes that of the prior art. Therefore, the present invention can indeedaccomplish quick transmission of detected image signals, and has outputimage signals with high strength.

Although the present invention has been described with reference to thepreferred embodiment thereof, it will be understood that the inventionis not limited to the details thereof. Various substitutions andmodifications have been suggested in the foregoing description, andother will occur to those of ordinary skill in the art. For instance,the number of the readout circuits and the amplifying circuits is notlimited to four. Moreover, the disclosed architecture can apply to imagesensing devices such as CIS modules or CCD modules. Therefore, all suchsubstitutions and modifications are intended to be embraced within thescope of the invention as defined in the appended claims.

1. An image sensing module capable of fast transferring signalcomprising: an optical sensor set having a plurality of optical sensors,said optical sensors being used for receiving an optical signal andgenerating a plurality of corresponding charge signals; a plurality ofreadout circuits each having a plurality of input terminals connected toa portion of said optical sensors and an output terminal, said outputterminals of said readout circuits outputting in order said chargesignals received by said input terminals; and a plurality of amplifyingcircuits each having an input terminal and an output terminal, each ofsaid input terminals of said amplifying circuits being independentlyconnected to one of said output terminals of said readout circuits;whereby said input terminals of said amplifying circuits receive andamplify said charge signals outputted in order by said output terminalsof said readout circuits, and said output terminals of said amplifyingcircuits then output said amplified charge signals one by one.
 2. Theimage sensing module capable of fast transferring signal as claimed inclaim 1, wherein said optical sensor is one of the photodiode andphototransistor.
 3. The image sensing module capable of fasttransferring signal as claimed in claim 1, wherein said input terminalsof said readout circuits are connected to said optical sensors in adiscontinuous way.
 4. The image sensing module capable of fasttransferring signal as claimed in claim 1, wherein each said readoutcircuit comprising: a switch array having a plurality of switchescorrespondingly connected to said optical sensors; and a shift arrayhaving a plurality of shift registers correspondingly connected to saidswitches; whereby said shift array turns on in order said switchesconnected to said shift registers to output in order said charge signalsof said optical sensors connected to said switches.
 5. The image sensingmodule capable of fast transferring signal as claimed in claim 1,wherein each said amplifying circuit comprising: an operation amplifierhaving a grounded first input terminal, a second input terminal and anoutput terminal; a first switch having a first terminal and a secondterminal, said first terminal being connected to said output terminal ofone of said readout circuits; a second switch having a first terminalconnected to said second terminal of said first switch and a groundedsecond terminal; a third switch having a first terminal connected tosaid second input terminal of said operation amplifier and a secondterminal connected to said output terminal of said operation amplifier;a fourth switch having a first terminal connected to said outputterminal of said operation amplifier and a second terminal; a firstcapacitor having a first terminal connected to said second terminal ofsaid first switch and a second terminal connected to said second inputterminal of said operation amplifier; and a second capacitor having afirst terminal connected to said second input terminal of said operationamplifier and a second terminal connected to said output terminal ofsaid operation amplifier.
 6. The image sensing module capable of fasttransferring signal as claimed in claim 5, wherein said second terminalsof said fourth switches of said amplifying circuits are connectedtogether.
 7. The image sensing module capable of fast transferringsignal as claimed in claim 5, wherein the capacitance of said firstcapacitor is larger than that of said second capacitor of each saidamplifying circuit.
 8. The image sensing module capable of fasttransferring signal as claimed in claim 5, wherein said first switch andsaid third switch of each said amplifying circuit have the sameswitching frequency and are synchronous.
 9. The image sensing modulecapable of fast transferring signal as claimed in claim 5, wherein saidsecond switch and said fourth switch of each said amplifying circuithave the same switching frequency and are synchronous.
 10. The imagesensing module capable of fast transferring signal as claimed in claim9, wherein said second switches of said amplifying circuits have thesame switching frequency but are not synchronous.
 11. The image sensingmodule capable of fast transferring signal as claimed in claim 9,wherein when said readout circuits output a charge signal, said secondswitches of said amplifying circuits will be on in order.
 12. An imagesensing method capable of fast transferring signal comprising the stepsof: providing m charge signals by detecting light; dividing said mcharge signals into n sets of outputs in a discontinuous order;capturing said charge signals of each set at the same time; andoutputting said captured charge signals in an orderly and time-sharingway.
 13. The image sensing method capable of fast transferring signal asclaimed in claim 12, wherein the division of said n sets of outputs isaccomplished with n readout circuits.
 14. The image sensing methodcapable of fast transferring signal as claimed in claim 13, wherein eachsaid readout circuit outputs (m/n) charge signals in order.
 15. Theimage sensing method capable of fast transferring signal as claimed inclaim 12, wherein the arrangement order of said captured n chargesignals is continuous.
 16. The image sensing method capable of fasttransferring signal as claimed in claim 12, wherein said captured chargesignals have been amplified before outputted in an orderly andtime-sharing way.